The paper describes new algorithm of detecting the fault location for the power lines 6–35 kV with unilateral feed. The results of operational control of the short-circuit current for the faulted phases are the only initial data needed for the fault location algorithm. Analysis of the impact of the type of short circuit, transition resistance at the damaged point, errors of current transformers, load of the line, power and resistance of supply system, calculation errors of short-circuit currents at the beginning and at the end of the line on the performance of this algorithm is also performed. Estimated parameters of the algorithm of detecting the fault location based on identified influencing factors were established by method of computational experiment. Analysis of the simulation results performed shows that the variation of the relative error in the fault location determination for different types of faults is about the same. Moreover levels of these relative errors from the effects of all influencing factors can be less than just from one of them. This is due to the mutual compensation of the various factors’ influence on values of relative errors. This fact must be taken into consideration when performing the corresponding estimates for the worst case scenario.

This paper presents the dynamic characteristics of this algorithm for detecting the fault location that allows estimating the time of detecting the fault location in different modes. Their analysis shows that there is almost no difference in quantitative and qualitative dependencies for different loads and types of faults. As the evaluation of results performed it should be noted that by means of the control only one parameter in short current mode, i.e. the short-circuit current, it is possibly with acceptable accuracy to detect the fault location.

 

The distributed power network 0,38–10 kV is investigated and the conditions for providing optimal load of network and technically reasonable (minimal) values of electricity consumption are determined. It is shown that the optimum (minimum) value of all technical losses of electricity in power network 0,38–10 kV is being achieved at the equality of semi-constant and variable (load) losses in network  and in denominated units for the period T and is characterized by twice value of variable losses. Optimum work load of transformers is determined by their technical data and is equal to (approximately) 40 % and corresponds to relatively low value of minimum losses – 1,73 %. In the whole, in network 0,38–10 kV there is optimal load factor for non-changeable equipment set, to a great extent, which depends on configuration and type of equipment. The more branching of network the less will be effective line’s resistance and so the value of optimal load factor will be more significant.

Networks 0,38 kV mainly influence on formation and value of total electricity losses in network 0,38–10 kV as losses in 0,38 kV networks under the equal conditions are higher than in 10 kV networks in times (or ten times). Losses in 0,38 kV network to a great extend decreases the value of generalized coefficient of network load and increases optimal value of relative loss in network 0,38–10 kV. And optimal total losses in denominated units are not changed. 

The developed structural algorithm of technical losses of electricity in network 0,38–10 kV allows evaluating actual and optimal network loading, to determine minimum and reserves of losses enhancement, but it can be realize only when loading of lines and transformers is low. That is why minimum technical losses are not finale criteria of optimal state of network which should be (in reality) determined from economical reasons, for example, from minimum cost of electrical energy transmission.

This paper describes an estimation method of decreasing losses of active power in power transformers with voltage 10(6)/0,4 kV after installation of devices of reactive power compensation on output side depending on voltage level, connected to capacity devices, taking into account dielectric loss in capacitors. Analysis of functional dependences was carried out. Investigation of function with a help of derivations was carried out. Points of function extremum and also its intervals of rise and fall rates were founded. This paper describes graphic investigation of obtained functional dependence, which is introduced by quartic polynominal. It is established that decreasing of losses of active power depends on technical parameters and load factor of transformer, coefficient of loading power of electricity consumers, voltage value connected to capacitor unit.

Using obtained functional dependences, calculations for the main size-types of power transformers with voltage 10(6)/0,4 kV serie ТМГ 11 and ТМГ12 were done. It is established that depending on technical characteristics of certain transformer, coefficient of its loading and power, there is a definite value of deviation of real voltage value from working voltage of capacitor installation when it will be observed positive technical and economical effect from installed capacitor battery unit. For taken value of loading coefficient and transformer’s power the maximum decrease of losses of active power takes place under voltage directed to capacitor unit, which is lower then nominal value. For all taken size-types of power transformers the argument of investigating function for its maximal value is out of standard permissible of voltage deviations from nominal value.

These functional dependents can be used for preliminary calculations, which are needed for making decision on compensation of reactive power in electric power supply systems of industrial objects. Their consideration allows more accurately evaluate technical and economical effect from installation of capacitor’s batteries in electrical networks with voltage up to 1 kV.

The aim of this work is to attract attention of teachers, scientific personnel, engineers and students to one peculiarity of extremum seeking in different electrical problems. This feature lies in the fact that in many parts of electrical engineering extremum seeking comes to analysis one and the same mathematical structure (T-structure), but differences lie only in many symbols (designation).In one problems this structure appear in finale, the most simple form, but in others – T-structure is “veiled”, and as a rule  we need  elementary algebraic transformation to detect it.

Taking into account high frequency of this structure appearing in electrical problems, in the first part of article the authors  carried out the investigation of extremum characteristics of T-structure and show the results in easy algorithms. To determine the typical T-structure there were taken five problems-examples for extremum seeking  from different parts of electrical engineering. The first and the second examples belong to the theory of electrical circuits.

In the first example the problem of maximum active load power obtaining was considered, in the second we see the solution of problem for inductive coupled circuit adjustment in order to obtain the hump current. In the third example the band active filter, built on operating amplifier, is analyzed. According to these methods, taken in the first part of article, the frequency is determined, on which amplifier provides maximum  amplification factor. The forth example deals with analysis of efficiency of transformer. According to algorithm, the optimal efficiency of transformer’s load and also equation for its maximum was determined in this article. In the fifth example the mechanical characteristics of induction motor is analyzed. It is indicated how, on the basis of algorithms article, to obtain equations for critical slip and motor moment, and also the simple development of formula Klossa.

The methods of contrastive analysis of equations for calculation of extreme parameters in different electrical problems were used in this article. And as a result, it was determined that there is the same T-structure in equations, and this allow to develop the single approach for extreme parameters determination. It was shown that looking of extreme parameters in many electrical problems leads to analysis of the single mathematical T-structure. On the basis of T-structure analysis was obtained the single algorithm of extremum seeking. These five examples from different fields of electrical engineering present, first, typicalness of T-structure, the second, the simplicity obtaining of extreme parameters on the base of algorithm.

The paper presents an analysis of several variants of energy-efficient solutions for hot water supply systems in Minsk buildings that ensure significant reduction of energy for hot water supply in comparison with the existing level. The different systems have been considered as technical facilities for usage of solar energy and secondary heat sources and which are based on heat recovery of “grey” waste water, solar collector, photoelectric transducer, heat pump.

Comparative analysis of the considered variants shows economic efficiency of waste water heat utilizers. An advantage of such system is in its all-year round usage in comparison with a solar collector. The second variant that is a combination of waste water heat utilizer and a solar collector that increases energy saving but it requires the increase of capital expenses. The third variant completely covers expenses of heat energy which is necessary for hot water supply. It is neces-sary to attract attention to the fact that expenses in the first two variants are close to the required ones but values of the third variant may significantly exceed the reliable level.

The paper contains analytical material of Belarusian and Vietnamese researchers who were actively involved in implementation of the joint Belarusian-Vietnamese project “Usage of Renewable Power Sources in Physical-Mathematical Model of Heat Regime of Energy-Efficient House” (Project code: VAST. HTQT. Belarus. 03/2012–2013).

 

In the process of automatic control system debugging the great attention is paid to determining formulas’ parameters of optimal dynamic adjustment of regulators, taking into account the dynamics of Objects control. In most cases the known formulas are oriented on design of automatic control system through channel “input-output definition”. But practically in all continuous processes the main task of all regulators is stabilization of output parameters. 

The Methods of parameters calculation for dynamic adjustment of regulations were developed. These methods allow to optimize the analog and digital regulators, taking into account minimization of regulated influences. There were suggested to use the fact of detuning and maximum value of regulated influence. As the automatic control system optimization with proportional plus reset controllers on disturbance channel is an unimodal task, the main algorithm of optimization is realized by Hooke – Jeeves method. For controllers optimization through channel external disturbance there were obtained functional dependences of parameters calculations of dynamic proportional plus reset controllers from dynamic characteristics of Object control. The obtained dependences allow to improve the work of controllers (regulators) of automatic control on external disturbance channel and so it allows to improve the quality of regulation of transient processes. Calculation formulas provide high accuracy and convenience in usage. In suggested method there are no nomographs and this fact expels subjectivity of investigation in determination of parameters of dynamic adjustment of proportional plus reset controllers. Functional dependences can be used for calculation of adjustment of PR controllers in a great range of change of dynamic characteristics of Objects control.

The main rules of computer models construction were developed, which intended for pipeline networks design and they were considered as single whole hydraulic systems. The construction of new sections is possible after their design in order to provide operation in given regime. In heat networks operation we see the following problems: irregular change in pressure between direct and return pipelines, increased pressure in return pipeline, misalignment of network and others. Their causes may be: undersize thickness of pipelines, reduction in diameter caused by scales in internal surfaces of pipes, closure of gate valves in sections of networks with big speeds of heat coolant, “parasitic” circulations and others. Efficient mean for determining the main reasons of these problems, they may be in any heat pipeline, and also for new heating pipe networks design we consider computer models, which allow to simulate (practically in the whole volume) hydraulic and temperature regimes of their work.  

The purpose of work – using computer models for implementation of project of new heat removal pipe from Tolyatti central thermal station in order to heat the Central Region of Tolyatti, feeding from heat power station of the Volga car factory .With the help of developed computer model the location of equipment and their main characteristics were determined, they take into account joint work of two sources of heat (central thermal station of Tolyatti and the Volga car factory).

 

The structure of pulsed layer is proposed which can be suggested as a state of particulates that is blown by intermittent gas flow with speed which has the force to start material moving. Layer during one cycle is in a suspension, falling down and immobile state resulting in changes of particles arrangement as well as ways of gas flowing through layer. Moreover, it allows carrying out effective interphase heat exchange even adamant real granulation.

The process of formation of impact flows is considered aw well as their influence on formation of air bubbles in pulsed layer. At startup of air blast the balance between the force of hydro-dynamic resistance is broken, on one side, and forces of gravity, particles inertia and their links with walls on the other side. The layer is transferred in the state of pulsed pseudo-fluidization, and presents gas-disperse mixture, inside of which impulse of pressure increasing is spreading to all sides as pressure waves (compression). These waves are the sources of impact flows’ formation, the force of which is two times more than during the stationary flow.

The waves of pressure are divided into weak and strong ones depending on movement velocity within gas-disperse system. Weak waves are moving with a sound speed and strong ones in active phase of pulsed layer are moving over the speed of sound limit within gas-disperse system. The peculiarity of strong wave is that parameters of system (pressure, density and others) are changing in discrete steps.

The article describes the regime of layer’s falling down in the passive stage of cycle, which begins after finishing of gas impulse action. And suspension layer of moving up granular material is transferred in the state of falling resulting in change of the layer structure.

Sufficient atomic power generation safety increase may be done with microfuel adapting to reactor plants with water coolant. Microfuel particle is a millimeter size grain containing fission material core in a protecting coverage. The coverage protects fuel contact with coolant and provides isolation of fission products inside. Well thermophysical properties of microfuel bed in a direct contact with water coolant excludes fuel overheating when accidents. Microfuel use was suggested for a VVER, а direct flow reactor for superheat steam generation, a reactor with neutron spectra adjustment by the steam partial content varying in the coolant.

Nonuniformities of two-phase coolant distribution in a heat generating particles bed are predicted by calculations in this text. The one is due to multiple-valuedness of pressure drop across the bed on the steam quality dependency. The nonuniformity decreases with flow rate and particle size growths absolute pressure diminishing while porosity effect is weak. The worse case is for pressure quality of order of one. Some pure steam filled pores appears parallel to steam water mixture filled pores, latter steam quality is less than the mean of the bed. Considering this regime for the direct flow reactor for superheat steam generation we predict some water drops at the exit flow. The two-phase coolant filtration with subcooled water feed is unstable to strong disturbance effects are found. Uniformity of two-phase coolant distribution is worse than for one-phase in the same radial type reactor.